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R-factors: Difference between revisions
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To my knowledge, the only program that implements this currently (December 2008) is [[xds:XDSSTAT|XDSSTAT]]. | To my knowledge, the only program that implements this currently (December 2008) is [[xds:XDSSTAT|XDSSTAT]]. | ||
=== Comparing two sets of structure factor amplitudes or intensities === | |||
The following is symmetric, and suitable for comparing two data sets, or two model amplitudes: | |||
<math> | |||
R=\frac{\sum_{hkl}\vert F_{hkl}^{i}-F_{hkl}^{j}\vert}{\sum_{hkl} 1/2 (F_{hkl}^{i}+F_{hkl}^{j})} | |||
</math> | |||
for amplitudes, and analogously for intensities: | |||
=== Model quality indicators === | === Model quality indicators === | ||
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<br> | <br> | ||
where <math>F_{hkl}^{obs}</math> and <math>F_{hkl}^{calc}</math> have to be scaled w.r.t. each other. R and R<sub>free</sub> differ in the set of reflections they are calculated from: R is calculated for the [[working set]], whereas R<sub>free</sub> is calculated for the [[test set]]. | where <math>F_{hkl}^{obs}</math> and <math>F_{hkl}^{calc}</math> have to be scaled w.r.t. each other. R and R<sub>free</sub> differ in the set of reflections they are calculated from: R is calculated for the [[working set]], whereas R<sub>free</sub> is calculated for the [[test set]]. | ||
==== Relation between R and R<sub>free</sub> as a function of resolution ==== | ==== Relation between R and R<sub>free</sub> as a function of resolution ==== | ||